Inductive communication system between moving vehicles and conventional telephone subscribers



May 16, 1950 E. w. MARLoWE INDUCTIVE COMMUNICATION SYSTEM BETWEEN MOVING VEHICLES AND CONVENTIONAL TELEPHONE SUBSCRIBERS 3 Sheets-Sheet l Filed Aug. 24, 1948 May 16, 1950 E. w. MARLOWE 2,507,728

INDUCTIVE COMMUNICATION SYSTEM BETWEEN MOVING VEHICLES AND coNvENTIoNAL TELEPHONE suBsCRIBEEs Filed Aug. 24, 1948 s sheets-sheet 2 14n/fm .Miles INVENTOR. Elbelt W Marlowe 1115 ATT '0R/VE Y May 16, 1950 E. W. MARLOWE INDUCTIvE COMMUNICATION sYsTEM BETWEEN MovINC VEHICLES AND CoNvENTIoNAL TELEPHONE sUBsCRIBERs 3 Sheets-Sheet 3 Filed Aug. 24, 1948 HIS ATTORNEY N mmm nu n n R1 \W ww U EEEV. uw X3 G atenteci May 116,

INDUCTIVE COMMUNICATION' SYSTEM' TWEEN MOVING VEHICLES AND CONVEN- TIONAL TELEPHONE SUBSCRIBERS Elbert W. Marlowe, ,Wilkinsburg, Pa., assigner ttf The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application August 24, 1948,#seria1No. 45,896

11 Claims.

My invention relates to communication systems for vehicles and more particularly to a system which enables a passenger on a vehicle. en route to telephone to an ofce remote from the trackway along which the vehicle is moving.

Facilities which provide telephone communica-'- tion between a passenger on a moving vehicle, such as a railway train, and a party at a remote ioce located olf the railway have been proposed. 'These facilities ordinarily include a space communication link to bridge the gap between the moving train and a wayside station and a yline .telephone link from the wayside lstation to the 4remote oice. The space communication link may be radio or inductive. The line telephone link may be the usual public telephone system. in such an arrangement frequent railway wayside stations with an attendant at each station rare required to enable a passenger on a train to telephone to a public telephone system subscriber from any point along the railway.

With this usual arrangement a conversatio between a passenger and a party at a remote ofice initiated through a given wayside 'station :along the trackway may be interrupted duev to fthe train advancing out of the range of trans` ,mission for the space communication linkwith that station. Thus, a long conversation may be interrupted onev or more times due to the train .advancing out of transmission rangewith the wayside station through which the connection is first established and connection to the telephone line circuit must be re-established through another station and this operation repeated as the train advances with the result that there are several interruptions in the conversation.

Accordingly, a feature of my invention is the provision of novel and improved communication systems for vehicles. V

Another feature of my invention is the pro vision of a communication system for vehicles incorporating improved repeater facilities to provide telephone communication between a passen- `ger on a vehicle en route and a remote ofce and which repeater facilities require only a few attended wayside stations. f Y.

Again, a feature of my invention is the provision of a communication system for vehicles incorporating improved switching and repeater facilities to enable the connection between a vehicle and a public telephone subscriber to be established iirst through one wayside station and then re-established through a second waysidestation as the vehicle advances without interrup- -tionoi the conversation and whichrfacilities insure that at no time will the communication energy fall below a required energy level.

Another feature of my invention is the provision of a communication'system' incorporating an improved repeater and control means 'to enable the attendant at eachof two wayside sta-- tions, one at each side of a repeater station, to direct the transmission from the repeater station toward his respective wayside station, and to enable eachattendant to lock out the other attendant from seizing control of the repeater sta'- tion, an indication being provided at each wayside station' showing. when the lockout means isin effect. f' ,-1

Other features, objects and advantages ofmy invention will appearl as .theY specification progresses. g The foregoing features, objects and advantages of my invention I attain by a novel and improved combination of'rspace communicationv apparatus, line carrier telephone apparatus, repeater facilities and switching apparatus to interconnect the space communication apparatus on vehicles moving along vthe trackwayl wtih the subscribers of a public telephone system. l, w

Preferably, terminal vwayside stations'` are located one at eachnend. of the stretch of track- Way and repeaterstations vare spacedl along `the trackway at intervals somewhat less thandouble the effective range' of the space communication equipment. vFor example, .if the effective range of the space communication equipment is lof the order of 30 tor35 miles, the wayside stations are located approximately 50 miles apart. Thus, for a trackway division' having a length of the-order of 200 miles there would be a terminal station at each end andthree repeater stations. Certain ones of theY repeater stations, which I shall term inter-mediate repeater stations, are arranged for eachto cooperate with the nearest terminalrstation and other ones of the repater stations, which I shall call overlap repeater stations,n are arranged to cooperate with the nearest terminal station in each direction. In Vthe example recited above, the rst onev of the repeater stations would be an intermediate repeater station which cooperates with a first one, say, the west terminal station, a second one of the repeaterstations would be an overlap repeater station which cooperates with thewest terminal station and also with the other or east` terminal station, and a `third one of the repeater stations would be an intermediate repeater station cooperating with the east terminal station.

, Each Wayside station and eachY vehicle iS advance or with the Wayside'V stationfto the rear.'

That is, the track layout of the Wayside'stations according to my inventionprovide's an overlap between stations for the space communication equipment.

The line carrier telephone equipment involvesV duplex carrier telephone apparatus at each 'wayfv side station and a line circuit which extends from` each terminal station through the adjacent intermediate repeater stationsV to the .overlapref peater station. The line carrier apparatus lof. each wayside station is connected Vto the line circuit for communicationbetween the wayside stations, and at each repeater station the line carrier apparatus is adaptable of being coupled to the space communication apparatus at the same station. The line carrier telephone at each terminal station is connected to the line 'circuit and it is also adaptableof being connected to a public telephone line connection.

The terminal wayside stations are attended and each is provided with a telephone line connection which terminates at the switchboard of an exchange of an associated'public .telephone system. By switching means to be referred to, the attendant at each terminal station of my inyen; tion can arrange with the operator at the'exchange of the public telephone system torconneet any subscriber of the public'telephone system and any toll line party with whom the public telephone system canV connect, to Athe space communication apparatus or to .the line carrier apparatus of that Vparticular terminal'station.

The switching apparatus includes line circuits for interconnecting the space communicationapp'aratusV and the line carrier apparatus of the dif-` vferent wayside stations and for connecting these apparatuses to the public telephone connections.

The arrangement of these line circuits is .such A that an4 operator at a terminalstation can selectively connect the 'space communicationapparatus or the line carrier telephone apparatus of his own station tothe public" telephone line connection of his station. It also enables the operator at a terminal station to electivelycouple the line carrier telephone apparatus of any one `of the intermediate repeater vstations cooperf ating with his terminal station or that atrthe overlap repeater station to the space communication apparatus of the respective repeater staf tion. In this way an operator at a terminal station can set up telephone connections from' any Vehicle to a subscriber of the'public system as long as the vehicle is betweenlhis terminal stad through the overlap repeater station and the other terminal station and the switching means provides such transfer of connections without an interruption of the conversation. That is to say, there is an overlap territory adjacent the overlap repeater station during Ywhich the connection between av vehicle and asubscriber" o'fthe public telephone system can be established from either terminal station. Accordingly, a connection bestation.

;l of equipment embodyingmy inven ne` tween a vehicle and a public telephone system subscriber first established through one of the terminal stations'can be transferred to the other terminal station by the terminal station operatrs while the vehicle is moving through the overlap territory 'adjacent the overlap repeater The switching apparatus also preferably includes lockout means wherewith an operator at either terminal station onceV having taken over the control of the overlap repeater station can prevent lthe operator et the .other tsrmilal ePation from controllirlg the overlap repeater exc as the two operatorsprearrange.

1 shall describe oneiorrn Qf apparatus embody,- ine my invention and Shall then @im but, novel features thereotinclaims,

In the`V ln@companyine drawings, Figs .1aI 1b. and 1c when placed end tgenclwtlifFig-"l et the left are diagrammatic views sli with a communication system for railw yA trai A.

It is to be understood that my inve .on 'is 'lt limitedvto communication systems `fo"r` railway freins and this one embodiment illustrates(- manyplacesthe equinmentisnseful! Referring to the drawings, the reference character TR designates a 4 stretchvoi railwaytracl .which `is .equippenwitn e train nomrnnnifan system :of the type here involved. Ihis trackll may be that of a single track line or it may one track` vof a multipletrack road. I shall sider the. track .TR as all veastbound track o f "a double track road extending between a west ,ter-l minal W` 'andk an east termirfial E, landv which terminals are spaced apart a distance of @m6101200 miles but. the. distance ,between @he terminals may vary according to the territory through which the railway runs, my invention. ,not .being -limited toany specific length of track.

'This Stretch 0f railway is here provided with five communication system stations designated as stations ALBI, DI, B2, and A2, and which stations are illustrated as spaced approximately :50' miles 'apart although a different number Aof stations andl other ,spallgs ,0.31.1 be. use@ stations Al vand Alare terminal ,wayside stations lo'cated at the railway .terminals W and respectively,V and stations Bl, Dl, andBZ are repeater Wayside stations, the stationsBl ,and;l32being intermediate repeater stations and the stationiDl being ran overlap repeater station,

Tlwo eastbound ,trains movlrigover Llaclr are shown conventionally at ATN] and TN2, train LTNI being in the `vicinity ,of the terminal station Al and train TN2 being a' short distance to the east of station DI. Y J

Erachoi the .wayside stations and eachoflthe vtrains are provided with space communication vequipment which may .be ofpthe radio type orof the inductive type, both such typesof train cornmuni'cation 'equipment being known in the art. As here illustrated .thefspace communication equipment a duplex,carrier inductive system, one carrier frequency, being ,used for transmission from the .wayside stations to the .trains and `a Second and different carrier frequency being used forV transmission from the trains to the wayside stations. As an aid in the understanding of the invention, I shall assume that a carrier of 140 kilocycles is used for sending from wayside stations to trains and a carrier of 80 kilocycles is used for sending from trains to the wayside stations.

Inductive carrier communication systems of the type here contemplated utilize a transmitting channel which is formed by the line Wires paralleling the track, the track rails, the distributed inductance between the line wires and ground, and the distributed mutual inductance of the line wires and the track rails. The reference characters LI and L2 designate a pair of line wires which extend along the track TR between the terminals W and E and which line wires are available for use in the transmitting channel of the carrier inductive communication system due to the longitudinal circuit formed by the line wires in multiple and their distributed impedance with ground. These line wires LI and L2 may be existing wires used in a telegraph or similar circuit and which are strung on a pole line along the railway to bring the wires substantially parallel to and relatively close to the track so that the line wires are capable of effective inductive relationship with circuit elements mounted on a train. equipments indicated conventionally by the refer- 'ence characters TLI and TLZ are located at'the Wayside stations AI and A2, respectively, and con- -nected to the line wires LI and L2 for telegraph communication between these two terminal stations in the usual manner.

The space communication equipment provided for each train includes a transmitter and a receiver. For example, the train TNi is provided with a transmitter and a receiver shown conventionally at SGKCT and IQIIKCR, respectively. The transmitter SBKCT is shown coupled to the transmitting channel through a loop circuit including a transformer TI, a primary winding 9 of which is connected to the output of the transmitter, and a secondary winding I of which transformer is connected to two pairs of spaced wheels of the train, and which loop circuit thus formed has an inductive relation with the transmitting channel including the line wires Li and L2. The receiver MGKCR is connected to a pickup coil II mounted on the train for inductive relation with the rails and line wires of the transmitting channel. The transmitter SBKCT and the receiver IiKCR may take different forms and they may be similar to the corresponding devices described in a copending application for Letters Patent of the United States of common ownership, Serial No. 575,311, filed January 30, 1945, now U. S. Patent No. 2,484,630, issued October 11, 1949, by Paul N. Bossart, for Railway train communication systems.

It is sufficient for this application to point out that the transmitter KCT is capable of supplying a carrier current of 80 kilocycles modulated by voice frequencies, frequency modulation being preferably used, and the receiver IllIKCR is capable of demcdulating and reproducing the voice frequencies of a carrier telephone current using a carrier of 14@ kilocycles and frequency modulation.

The space communication equipment at each wayside station includes a receiver SBKCR and a `transmitter MSKCT, and which devices are `similar to the train carried devices except the As shown in the drawings, telegraph station transmitter uses a. carrier of 140 inlo-4 cycles to cooperate with the train receiver using 140 kilocycles, and each station receiver uses a carrier of kilocycles to cooperate with the train transmitter using a carrier of 80 kilocycles. In this way the wayside apparatus and the train carried apparatus provide duplex operation. These wayside station devices for the space communication equipment are coupled to the transmitting channel by being coupled to the line wires LI and L2 in multiple. For example, at the terminal station AI, an output transformer T2 has its primary winding I2 connected to the output of the transmitter I40KCT, and a secondary winding I3 coupled to the line wires Li and L2 in multiple by having one terminal connected to the junction terminal of two capacitors I 4 and I5 connected in series across the line wires LI and L2, and its other terminal connected to a ground electrode Iii. An input transformer T3 has its primary winding I1 coupled to the line Wires LI and L2 in multiple with the secondary Winding I3 of transformer T2, while a secondary winding I8 of the transformer T3 is connected to the input of the receiver 8IJKCR.

Thus when the train TNI is within the range of station AI, carrier telephone current supplied by transmitter BDKCT on the train is transmitted through the transmitting channel including the line wires LI and L2 and applied to receiver BFJKCR. at station AI and a corresponding voice telephone current appears on the lead wires I9 and 2E) connected to the output of the receiver. Also, fa voice frequency current applied through wires I9 and 20 to the input of the station transmitter IdKCT when that transmitter is made active in a manner to appear shortly is converted to a carrier telephone current of kilocycles and transmitted to the vehicle through the transmitting channel and picked up by coil iI and applied to the receiver I liDKCR and the corresponding voice frequency energy is reproduced in the output of that receiver.

It is to be observed that the receivers of the space communication equipment are all normally active, that is, each receiver is active during noncommunication periods ready to receive a message. The transmitters, however, are normally inactive but are conditioned so as to become immediately active when energy is applied thereto from a proper source. For example, the transmitter IKCT at the terminal `station AI immediately becomes active when energy from a. source having a terminal 300B is applied thereto by the closing of a manually operable switch 2l and back contacts 9| and 92 of relays BIR and DRI to be referred to later.

The line carrier telephone equipment comprises a carrier telephone transmitter and a carrier telephone receiver at each Wayside station together with a line circuit between the stations. For example, a pair of line Wires L3 and Lil extend between the West terminal station AI and overlap station DI and also between the east terminal station A2 and station DI. At station DI these line wires are preferably dead-ended although they may be connected by filters to permit their use in other circuits if desired. The line carrier telephone transmitters and receivers at the wayside stations may be of any one of several forms which will enable duplex operation between each terminal station and the cooperating repeater stations. Looking at station AI, the line carrier telephone equipmentincludes atransmitter and a receiver LShawn ,conventivnally atSSKCT and licences SKCR; respectively-f, the transmitterrusingacar@- rierof;35 kilocycles and the'receiver using ae car:- rier: of ef'kilocycles.. The: outputfo the trans;- mitter- SSKCT and: the` input of; the: receiver SKCBJL at station AI' are` connected multiple across:r the line WiresIL and Lr through! an outfpuii. transformer Tlland an input. transformer '155; respectively, as will be` apparent. byfanainspece tion-,of the drawing,;blocking capacitors`22-"and'2f'3 being, preferably interposed. in the connection;

At. the terminal station. A2` the lineJ carrier telephone transmitter amt receiver `are thersame as ai?. station All. At. the repeater: rstations Bit D;l and; B21, the line. carrier-` telephone equipment includes a transmitter. -AEKCT anda yreceiver 35KCRLsimilar. to: those of the termina-l'fstations except thetransmitter usesa 45 kilocy'clezcarrier tocooperate with the-terminali station2 fii'iKCR receiver and. there'ceiver usesf-a 35 kilocycl'e car'- rier tocooperatewith: the terminalzstaticntransfmitter BFIKCT.

the overlap repeater` 'station Dt, .there line carrier telephone equipment preferablyincludes `a transmitter' and a receiver associated with the line Wires L3 and L4` extending West-tor'tlie:ter=` minal station Ai" and also a receiver-andaftransmitterthatv cooperate'with the line .Wires-L3? and E32-extending east to the terminal station: A2;

At each o1" the terminal stationsf'Al vandi A2 the line carrier telephone equipment'is.adaptable ofv being connected toa-linet'elephone' connection of a publict'eleplione system throug-lrthexswitch'.- ing apparatus and thatiat' each' repeater station is adaptable of' being coupled-to the space conrmunication equipment through lconnections under thecontro'lof the operators at'the terminal staaf tions by'I the switching apparatus: aswill now.' b'e described. n

At stationAI; a jack typeconnection-'l leads to an exchange office oian associatedpublictelephone system and thus an'` operator at'v 'the exchange oiice f. can arrange to connect any-'sub1 scriber or toll line party tothe connecticnl *of station Al ofthe trainv communication: system. Similarly, a jack connection S3 at station A2 leads to anfexch'ange office of the public telephone system for connection to' the subscriber-sofi' the public telephone system. Y

The switchingapparatus involves two line-con.- trol circuits .extending` from eachlterminalstation to the repeater stations, these `line control circuits usingthe line wires L32 and! Lil', althoughzother linewires-r may be used. Each terminal station operator has charge off set-ting 'upfthe'telepho'ne connections between trainsf and-'subscribers'ofthe public telephone system by. use of!theswitching,r apparatus. Each operator arranges theconnec'fvtion individually wheny the train isawithinlthe vicinity of'his terminal: station-or ai cooperating intermediate repeater station. Theg overlap repeater station is under the controliof both operators to enable a connection between a train vand ar telephone subscriber to be switched'A 'from- 'one terminal station to the other.. terminar` station by a--j oint action'othe t'wooperators.

.Considering first' the terminal station AI, a rst line control circuit extending' ther'efrom to the repeater stations isoi the polarized type arrd loops through the repeater stations .i1r..multiple'. This first line control circuit-fromtstation-Al is controlled by a selector key 24'Whichismanu'all'y operable from a center position-to either-a leftlhand; or a right-hand position a-nd when operated to the left-hand position it completes al simple v,circuit forl energizing acontrol` relay BiR and that relay is picked up.. Withhrelayf Btl?. picked 11p-the. line circuit is completed. for energizing control relays: at stations Blf` andA DI.'v byr energy supplied: from a battery 2.5 at station- Aft which linev circuit can" be traced from battery 1215 throughrfrontl Contact 2.6. of relay B'IRi,.,a=;simplex coi'laZ-' tothe two linewiresL3 andL4- in multiple. the two line Wires, a simplex coil 28 at stationsBl, windingfof 'af con-trol relay 29 tongroundz electrode 3B:,..=ground path ands ground electrode,I 3.1 tof-the other terrninalv of.v battery' 25 through. front coriitactl32" of. relay BI-SR.` At station DI thisfcircnitiis completed through simplex coil 33; the windings inls'eries ortwo-relayssll and 3,5: and ground-elec@- trode 36'. With. the selector y2liE moved 'to the right-hand position; aesimple circuity is completed for relay DR lf andthat relay is picked-up closing frontfcontacts 3?! and' 38 to pole change'the necti'on of battery v`25 tothev line wiresv L-and-flw. The control-relays 29, 34, and 35 at thefrep'eatr stations varefo'f the A bia-sv .polar type, thelcontacts of whichar'e-operatedv by-a bias element toa-prei selected position-and als'ocpera-ted` to this position whentliefrelay is-energized at one polraritya'ndftne contactsarefoperated to theother yposition--against the' bias 'When/the" relay is energized at the rever'se polarity. The arrangement isl such that W-lie'nl relay BllR is picked' up currentv offV whaztgI Shall cal'lf positive polarity is supp-lied trombate tery25 to the line circuit and the relays 29 and 35' Vare' energized required to shirt their com tacts 'tothe right-hand 'position but; the. relay-3l iS-'enerlgized tofhol'dits contacts infits biased-rightli'andposition. When'A relayvDRl is energizedglthe line' circuitlcurrenti's of negative polarity an'dltlre relays 29 and 35 are energized as required tokr'e tai-n theirl'contact's at the biasleft-handl position but relay- 311'L isi-energized toY shift its contacts'lto thel left-hand position.

Similarly, a polarized Aline control circl'iitze'mtends from terminal station` A2 vto the stations-:B2 and'Dli, the circuit-involving a selector -k'eyf 39, a battery 40 and contr'olrelays DR2 andi B2Rat theriterminal station' A2, line Wires L31 ancll? Lb, simplex'coils 4l,;801,and 81 and controlrelays 42, 43; andi-1MLv atftlfie repeater stations B2il andlxDt. The arrangement is suchthatwhen selector key 3-9f-is shifted to the right to pick up relay' B2B by a simplecircuit, battery 4U is connected?tothfe lin'e circuit at a-pola'rity as required tol energizeI relays'v l2 and '44' to shift their positions' and 'to retain Vrelay- 4'3 in its biais position, 'andi when selector 39`is shifted toftheleft-hand positionlto energizel relay DRZ- thev battery lill-is connected to2 the line at a polarity7 as required to shift .the rela1y-l to its rightehand position and to'retain the control relays 4f2v-and44` at'tlieir biased'rig-ht'- hairdvv positions.

Thesecondcontrol line circuit extendingfrom each-terminal station includesthe linewresLS and? L14; in vaV series or transverse circuit `andsources of different carrier frequency currents.Y Again', looking atlterminal station Al, the clos-ing'of a manually operable key 45 completesv a simple circuit Afor applying power to an oscillator the yconnection also including a. back contact of av lock relayLRl tobe referred to later'. The oscillatorl 'IKCT may be ofl any standard fo'rn'i such'as ari-electron' tube oscillator andfit' adapt; able of supplying a given carrier current Whichfl shall assume is of a frequency of '7 kilocycles'. The output ofthe oscillator is connected to the line Wires L35 and L4 throughatransformer 'lit andcapacitorsZ-Z andl 23. At stationllA arst 'or'rwe'st' 'receiverindicatedfconventionallyfat JKGR is responsive to a carrier frequency of 'i kilocycles and it has its input connected across the line wires L3 and L4 through a transformer T6 and its output connected to a control relay 41. Thus the relay 41 is energized and picked up in response to the oscillator 'IKCT being activated by the closing of the switch 45. This second control line circuit for station AI also includes a West oscillator IKCT at station DI and a receiver ISKCR and relay LRI at terminal station AI. The west oscillator I5KCT is of a standard form adaptable of supplying a carrier which I shall assume has a frequency of kilocycles when its input is supplied with power by a connection which includes front contact 48 of a relay 49. The output of the transmitter I5KCT is connected to line wires L3 and L4 to the west of station DI through transformer T1. The receiver I SKCR at station AI is responsive to a carrier of a frequency of I5 kilocycles and is'connected across the line wires L3 and L4 through a transformer T8 and has its output connected to the relay LRI through back contact 89 of relay DRI so that relay LRI is energized in response to energy supplied by the west transmitter I5KCT of the station DI providing the relay DRI has not been picked up.

Similarly, a second control line circuit including the line wires L3 and L4 ln series extends from a terminal station A2 to the repeater station DI. An oscillator shown conventionally at 1KCT at station A2 is controlled through a manually operable key 82 and back contact 6I of a lock relay LR2 for supplying energy to the line wires through a transformer T9 for energizing a second or east receiver 1KCR located at station DI `and connected through a transformer Tl to the line wires L3 and L4 to the east of station DI, a relay 49 being energized by this 1KCR receiver. Also a second oscillator I5KCT at station DI supplies a carrier of 15 kilocycles across line wires L3 and L4 to the east of station DI through a transformer TI I, and this control current energizes a receiver ISKCR. at station A2 through transformer TI2 to ln turn control relay LR2, relay LR?. being a lock relay for the station A2. The second oscillator ISKCTat station DI is activated through a connection including front contact 6D of relay 41.

In describing the operation of the apparatus I shall assume that the apparatus is at its normal condition, that is, the condition during noncomrnunication periods, and in which condition it is illustrated in the drawings. I shall next assume a passengel` on the train TNI places a call for ajsubscriber on the public telephone system. At the outset the passenger or an operator on the train acting for the passenger conditions Athe train transmitter SQKCT to send out its given calling signal, which may be the carrier modulated by a tone frequency of, say, 1000 cycles per second interrupted at the frequency of times per second. The carrier of the transmitter BRKCT modulated by the calling signal is supplied to the transmitting channel including line wires LI and L2 and energy is picked up by the receiver BSKCR at station AI, the train TN! being within the eiective transmission range of` that station. After demodulation at receiver 8`I1KCR the signal is applied through wires I9 and v.2li to the ringer of the telephone set 5i). The station AI operator answers thefcall by closing switch 2l to energize the inductive carrier transmitter IliIlKCT and then sending an agreed salutation to the train through the set 5i! and the transmitter IAUKCT. This carrier telephone current is picked up by the train receiverA I4llKCR and the current demodulated and the answering call reproduced on the train. The train operator then places the passengerscall With the station operator, who in turn then plugs in at the connection 5I to call the operator at the exchange of the public telephone system, who in turn will make the connection with the subscriber being called in the usual manner. When this has been done, station AI' operator will tell the passenger on the train that his party is ready. It is to be observed that the .public telephone system connection 5I is connected to' the input of transmitter I fiKCT and to the ou`t'A put of the SilKCR receiver of the inductive car-f rier equipment through back contacts of the two` control relays BIR and DRI, back contacts 53 and 54 being interposed in one side of thecircuit connection and back contacts 55 and 5E .being interposed in the other side of the connection.

From this point on the voice frequency tele--v phone current from the public telephone sys.

tem is applied to thetransmitter I 4DKCT and" the resultant modulated carrier telephone current transmitted to the train through the transmitting channel of the space communication system. The current is picked up and dernodulated at receiver IllKCR on the train and the voice frequencies of the conversation are reproduced, by the associated loud-speaker or other tele'-, phone receiving device. The return portion of the conversation is applied to the train transmitter SIIKCT and the modulated carrier` telephone current is transmitted to station AI. through the transmitting channel and is .ap--4 plied to the receiver SliKCR Where it is demodulated and the voice frequency telephone current.

is applied to the line leading to the public tele-Y phone system through the connection 5I. If necessary the station AI operator can monitor the communication through his set 50 inthe usual manner. y

If the conversation lasts for some little .time and the train TNI in moving east is getting out of the range of station AI and into the range' of the repeater station BI', the operator at Station AI will shift the connections to the re-l peater station BI. To do this, the operator at station AI shifts his selector switch 24 to the left to pick up the control relay BIBl which con. nects battery 25 to the line circuit to energize relay 29 to close its contacts 51, 58, and 59 andthereby energize transmitter Itt'KCT and cou--A ple the carrier telephone receiver 35KCR at station BI to the inductive carrier transmitter'l MBKCT, the carrier telephone transmitter 45KCT being permanently coupled to the inductive carrier receiver BQKCR. With the relay BBR picked up, the inductive carrier equipment at station AI is disconnected from the public telephone connection 5I at the back contacts 53 and 55 of relay BIR, and the line carrier receiverr 45KCR and transmitter 35KCT are connected to the pub# lic telephone system connection 5 I' through front contacts 53 and 55 of relay BlR. Also trans-V mitter I4BKCT at station AI is deenergized due to the opening of back contact 9I of relay BIR. Furthermore, the relay 35 at station D! is also operated by the line circuit but the operation of this relay at this time performs no useful pure' pose. From this point on the voice frequency energy from the public telephone system is supplied 13 35KCT to the inductive carrier receiver 8DKCR and transmitter I4BKCT, respectively, since back contacts 11 and 18 of relay 41 are now closed. At the same time the closing of back contact 6| of relay LR2 applies power to the 1KCT transmitter at station A2 and relay 49 at station Dl is energized and picked up opening back contacts 10 and 1l to disconnect the west line carrier transmitter 45KCT and receiver 35KCR from the inductive carrier receiver SUKCR and transmitter MBKCT at station Dl. This completes the transfer of the connection from the train TNI to the s-ubscriber of the telephone system. It is,`

to be noted that when lock relay LRZ at station A2 was released the lamp E4 was extinguished to indicate to the operator that the transfer hadY been made.

Thus the voice frequency telephone current from the public telephone system is now received through connection 68 at station A2 and applied to the transmitter SiiKCT over front contacts 8l and 88er relay DR2 and the carrier telephone current is sent out over the line circuit to station DI when it is received at east receiver 35KCR and the voice frequencies are in turn applied to the inductive carrier transmitter I4DKCI to be transmitted to the train, The return carrier current sent from the 8i! KCT transmitter on the train is picked up at the BEKCR, receiver at station D! and demodulated and the voice frequencies applied to the east line carrier transmitter 45KCT tobe sent to station A2 over the line circuit where the current is received and demodulated at receiver 45KCR and the voice frequency current is supplied to the public` telephone circuit through the connection 68.

When relay il... at station DI is energized in response to the transfer of the connections, the closing of front contact 4B applies power to the West transmitter IEKCT and the corresponding carrier current is supplied over the line control circuit to the i KCR. receiver at station Al and the lock relay LR! is energized and pickedup opening back contacts $5 and 88 to prevent the operator at station A! from control oi station DI, the lockout being indicated by the lamp 90 at station AI. When the lamp il@ is illuminated to indicate that the transfer oi the connection is completed the operator at station Al would restore his selector key 24 to its center position and restore the control relay 35i at station Dl.

n If the conversation continues as the train moves east toward the terminal station A2, the operator in station A2 can transfer the connection from the line carrier apparatus at station DI to that. at the intermediate repeater station B2 and then later to the inductive carrier apparatus of his own station A2 in substantially the same manner as the operator at station Al makes the transfer of the connection from station AI to the repeater station BI and then to the station DI except that the operation of the transfer is in the reverse order.

In the event train TNI is in the vicinity of the repeater station Bl when the passenger places a call,` the call sent out from the train through its transmitter SQKCT will be picked up at the receiver SQKCR at station BI and demodulated and the call signal applied to the line carrier transmitter 45KCT at station Bl which is nornially active so that the resultant call will be transferred to station AI through the line ciruit to be received at the receiver 45KCR at station Al and the call signal sounded at the set 19; The operator at station AI using his set 19 will 14 answer the call and place the call through the exchange of the public telephone system and thereafter arrange for the connection substantially in the same manner as explained hereinbefore.

In the case a passenger on the train TN2 which is near station DI places a call, the call will normally be directed from station DI to the east terminal station A2 due to a special connection provided at the station DI. The output of the receiver KCR at the station Dl is provided with an alternative connection which includes the input of the east line carrier transmitter 45KCT, a normally closed contact 83 of relay 44 and back contact 11 of relay 41. Thus the call from train TN2 will go from station DI to the east terminal station A2 to be received at receiver 45KCR of that station and the call sounded in the ringer of the line telephone set 84 of station A2.

In the event the train TN2 advances east and its conversation is still being carried on through the repeater station B2 and the train TNI has advanced east to be near station DI and the passenger on the trainTNI places a call, the call from train TNI will now be directed to the West terminal station AI because the line circuit to the east station A2 is already in use. This is so because the operator at station A2 in setting up the connection at station B2 for the train TN2 also operated the relay 44 at station DI to open its contact 83 and close contact 85, and the output of the inductive carrier receiver 8UKCR at station DI is switched from the input of the east transmitter 45KCT to the input of the west transmitter 45KCR at station DI,l the latter connection including a normally closed contact 86 of relay 35. These two relays 35 and 44 permit the two' operators at stations Al and A2 to direct thecon'- nections of a train in the overlap territory at station DI toward either of the two terminal stations but not toward both stations at the same time.

It is obvious that the two intermediate repeater stations Bl and B2 may be omitted and only the overlap repeater station Dl provided when the stretch of railway involved is of the length only a little greater than twice the effective range of transmission of the space telephone equipment.

It will be apparent from an inspection of the drawings taken in connection with the foregoing description of the operation of the apparatus for trains moving east that the apparatus will function in a similar manner for providing connections between a passenger on a train and a public telephone subscriber when the train is moving west over the west bound track or even when moving west over track TR.

Although I have herein shown and described but one form of communication system for vehicles embodying my invention it is understood that various changes and modifications may be made therein Within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my-invention, what I claim is:

1. In a communication system for telephoning between a passenger on a vehicle moving between two terminal stations of its trackway and a party having access to a bidirectional line telephone system by space carrier telephone equipments when the distance between said terminai stations is relatively great compared with the effective range of transmission of such space carrier tele phone equipments, a repeater station located along the trackway approximately midway 'betweexrsaidi terminal stations; saidi terminal sta tiene.; vehiclesand: repeater l station each provided. withi mid'snaceoar-rien telephone equipment;J aconnectiom o fsaid linei-telephonesystemat eachsaidi terminal station; switching means-, including aseiector at each terminalstation, afpair of, con-` trolreiays: at saidjrepeater stationzandia line cir/- cuitr between-V said terminall stations andv said: re-A Deater; Station-.fon controlv of saidrelays byisaid. Selectors; and means governedV by..- said: selectors and relays4 to eithery sole@tivelyv 'placefv thevr space carrier'teiephonefequiprnenti.ofV aggiyen one of the terminali stationspr.: that of; said. repeater station incommunicationirelationship with ther-line tele-` phone system connectiom or said giventerminal` station: on to; selectivelyI placethe space carrier telephone equipment. of;` the other terminal.V sta-- tion or that firmaid-'repeater stat-ionin:communil cation; relationship with the,l line-V telephone systempoonnection ofi saidother .terminal station.

.2i Iini a communicationfsystem yfor telephcningv boiiweeniaz. passenger 'onia! vehicle .moving Vbetween terminal staticnsef titsstrackway and a party having; access. to. a bidirectional line telephone system; by a-. space. carrierl telephoneV equipment whenL the distancefbetween said terminal-Stations isfover twice the effeetiveirangeoff transmission. onsaid;spaceftelephoneiequipment,.a-repeater sta.-

tunfloeated along@theftraokway. between saidter.- f

minalrstatons-te formfan-.orerlap between the repeaterfstatiom andfeach terminalstation for 'said` space telephone equipment; said terminall stations, vehiclev and repeater. station each providedi with said space telephonev equipment;` a connection' Ot Said-.line telephone system atfeach said terminal: station, switching means` for each said' terminal:- station,A eachrsald. switching. means including.l ai manually: operablev selector at the terminal station? andi acontrolrelay at .the repeater stations means controlled. by eachisaid switching means to selectively connect either the space telephone, equipmentat.. the, respective terminalI stationior thatat saidrepeater-station to the line telephone. system .connection at. thel same terminalgstation te enablesanroperator at either stationL toj establish. communication .between av pase sengerof: said vehiclelr and= a. party. connectedto the line telephone. system when, the vehicle. is betweenhis` terminal` station and.Y the repeater station. and,v other. communication. means includingga linecircuit extendingJbetween thetermlnahstationsand relaysat the.. stations to e11- ahlesthe, Operators to. cooperate in transferring theconnection establishedbetween the. passenger andadparty from onatermnal station tothe 5 between. a. passenger on. a vehicle moving over afgivemstretch of;atrack.way, and aparty 01T the tracleway. whensaidstretchis ofl a length greater thanJ twice agiven. range. oftransmission, tw-o terminal wayside stations one at each end @f sad stretch, a. repeater wayside,stationlocated. approximately midway between said terminal.. stations, ,space carrier telephone. equipment at' each of said. wayside` stationsandonrsaidr vehicle. and operative for4 eiective; communication. between saidfvehicle and awayside stationwhen the vehicle" is: within said given range of, transmission of the respective4 wayside station,- line circuit meansv extending; betweenVV said terminal stations and;said repeater station, ,each said `terminal4station, provided w-ith-I atelephoner connection through `each of, which connections a party off the trackway can be reached; 'switcl'iingV meansi izr-f cludingY a manually' eperableselector ateach-y of. said terminal. stations f and control i relays'. at.- said. repeater station,y and said switchingnieansfhaving.A connections to -said `line circuitv means` to enable. an operator at each of the terminalfstationmto couple either said carrier telephone equipments. of: his terminal` station or that at said repeaterstation to said telephone connection ofv hsterf minal station.

4. In a communication system for telephoning. between a passenger onavehicle movingover, a given stretch of av trackwayv andaiparty. oi. the. trackway when said stretch isof a lengthgreaten than twice.- a given range o1,- transmissiomtwo terminal waysidestations one at each end ofrsaidl stretch, a repeater wayside station located an:k proximately.- midway between said` terminalstations, space carrier telephone eouipment.at` each of said-,wayside stations and on said vehicle and operative for effective communication between. said vehicle and a wayside stationwhen the ve.- hicle is within said given range of. transmission of the respective wayside station, a public tele.`

phone system connectionat eachof saidterminal stations; switching means includinga sourceol power and a selector ateach terminal station, controlk relays at said repeater stationand'line wires extending between the terminal. stations and the repeater. station; and means including contacts of saidv selectors and contactsof` said.

control relays to enable an operator at eaohzof. the-terminal stations to selectively connect the space carrier. telephone equipment of histerminal i stationior thaty of. the repeater station tothepub.,

lic telephone system connection of his terminal. station.

5. In. a system for telephone communication between a passenger on a vehicle moving over a givenstretch of. its traclcway and a party offthe trackway by space telephone equipment when said stretch is of. alength relatively great. come pared with the effective range of transmission ofv said space telephone equipment, two terminal wayside stations one at each endof saidstretch and each. provided with a telephone connection through which a party oii the trackway may, be reached, a. plurality of repeater waysidestations located along the stretch and spaced so that the distance betweenany two adjacent wayside stationsis lessthan twice the e-iectivetransmission range of said spacetelephone equipmentspace telephone equipmentonsaid vehicle and one. at. each of said terminal and repeaterv stations, switching. meansfor each of said terminal sta: tions; eachsaid switching means including a mulev tiple position selector. and a-` current. source at the respective terminal station and a controlxe.- lay4 at eacnrepeater stationv counting from the respectiveterminal.station up. to and including agiven overlapstation of said repeater stations; means controlledby saidselector and relays of each said switching means to enable an oper-.- ator for the respective terminal station. to connectrei-ther the space:telephone-equipment ofthe respective terminal stationA or that at any one of; the repeater stations provided with a control relayvofthat switching means in communication relationship with said.- teleph-one connection. 0I the. respective terminal station, and other -switchA ing means rlocated partly at each saidzterminal stationiand including'other relays at saidtoverlarpv repeater-:station toen-able the: cperators for the twoiterminal stations to cooperative in` determine. ing.: to;V which of. the terminalstations telephonel 17"" connections the' space telephone equipment of said'loverl-ap repeater st ation is to be connected.

f 6. In kaV system for telephone communication between a" passenger on a train moving over a given lstretch of railway and a party 01T the railwaywhen said stretch is of a length greater than twice a given range of transmission, two vtermie nalV wayside stations one .at each end of said stretch and each provided with a telephone connection to enable telephoning from the terminal station to a party oi the railway, an overlap wayside station located approximately midway between said terminal stations, a space carrier` telephone equipment at each of said wayside stations and on said train and capable of effective communication between a train and a wayside station when the train is within said given range of transmission of the respective wayside station, aline circuit extending between each said terminal station and said overlap station, switching means including a control current source and a manually operable selector at each said terminal station and control relays responsive to said control current at said overlap station, and said switching means having connections to said line circuits to enable an operator at each said terminal station to couple either the space carriernal station, said lockout means connected to said'v line circuits to enable the operator at each terminal station to control the respective'other control relay, and means governed by each said other' control relay when operated to prevent the operator of the opposing terminal station from con" trolling the space carrier telephone equipment ofthe overlap station.

7. In a system for telephoning between a passenger on a train moving between two wayside terminal stations and a party off the railway through inductive carrier telephone equipments located one on the train and one at each of said terminal stations and which equipments have a given normal range of transmission along the railway, a stretch of railway greater in length than twice said given normal range of transmission, a terminal station at each end of the stretch, an overlap repeater station along the railway substantially midway between the terminal stations, an inductive carrier telephone equipment located at said overlap station, a public telephone system connection at each said terminal station capable of connections to parties 01T said railway; a switching means for each said terminal station including a control current source and a manually operable selector at the terminal station, a control relay at the repeater station and a line circuit between the terminal and repeater stations; means governed by each switching means to selectively couple the inductive carrier equipments of the respective terminal station and of the repeater station to the public telephone system connection of the respective terminal station, and other communicating means between said terminal stations to enable the operators of the terminal stations to cooperate in the control of said overlap station to maintain without interruption telephone connection between a passenger of the train and a party off the railway throughout the entire stretch.

8. In a train communication system using an inductive carrier .telephone equipment for tele-,i phoning-betweentrains and wayside stations for av given range of transmission, the combination comprising, a stretch of railway having a length greater than twice said given range, a terminalstation located at eachend of said stretch and an overlap repeater station at substantially the mid point of the stretch, each said station provided with said inductive carrier telephone equipment totelephone to trains when within said given range of the station, each said terminal station provided with a telephone system connection, a pair lof line wires extending between each said terminal station and said overlap station, each said terminal and overlap station provided with line carrier telephone apparatus connected to said line wires for transmission between the stations, manually operable switching means at each ter-l minal station to selectively connect the inductive carrier telephone equipment or the line carrier, telephone apparatus of the same station to saidI telephone system connection of the station, and other switching means including a current source and a manually operable device at each terminal' station and control'relays at said overlap station connected to saidline wires to enable an operator at either terminal station to couple the inductive carrier telephone equipment of the overlap station tothe line carrier telephone apparatus of the overlap station and to direct transmission*y from the overlap station line carrier telephone apparatus toward his respective terminal station.`

9. .In a train telephone system using train carried telephonek equipment having elements in ductively coupled to a longitudinal line circuit extending along` the railway, the' combination comprising, two terminal wayside stations locatedA at spaced points along the railway and each provided with public telephone line circuit connec' tion, another line circuit including a pair of line Wires extending between said terminal stations; a first, a second and a third repeater wayside station spaced along said railway between said terminal stations; each said terminal and repeater station provided with train telephone equipment coupled to said longitudinal line circuit for communication with a train when within the vicinity of the respective station, each said terminal and repeater station provided with carrier telephone equipment having connections across said pair of line wires, manually operable switching means at each said terminal station to selectively connect either the train telephone equipment or the carrier telephone equipment of the same station to said public telephone line circuit connection of the same terminal station, other manually operable switching devices located partly at said repeater stations and connected by said pair of line Wires in multiple and ground for an operator at each terminal station to eiectively cople the carrier telephone equipment of the adjacent and second repeater stations to the train telephone equipment of the respective repeater station, and additional switching means including relays located partly at said terminal stations and at said second repeater station and a manually operable key at each terminal station and connected by said pair of line wires arranged as a transverse circuit for the operator of either terminal station to lock out the operator of the other terminal station from coupling the carrier telephone equipment of the second repeater station to the train telephone equipment of that repeater station.

l0. In a communication system for telephoning atentos i between a passeneercn avehieie iiiotig between tions, vehicle and repeater station each provided with said space vcarriertelephone equipment: a' public telephone connection at each said terminal station through which anopeiat'r Aat the terminal station can inake connection With- 'subscribers of the public telephone system, switching/means incliidin'g a -niani'ially operable selector at Teach 'terminal station and control rela-ys at said repeater station there being one "ie'ia'y for `'ea'.eli selecto?, means governed fbyeach selector and its' respective control relay t0 selectively fcorict the /Siace telephone equipment of the respective terminal station or that at theiepeater station income munication relationship withn the public tele-v phone system connection '0f the respective terminalstation forA `c'ormnunieation between a ve'- hicie passenger and"a1-public telephone system subscriber,V and meansrlocated partly at each ter-'- minalstation and including aline cir'ciiit between thetwo terminalstations to enable the operators at the terminalfstations to transfer the connection between a passenger and a Subscriber 'from one terminal station tot-he other' terminal Station with substantially no interruption to the communication when the vvehicle'istvithin4v range ofV saide` peaterstation.

f1-l. In acommunication systemfor telephni between a passenger on a vehicle 'movingxbetween two terminal stations Aof its trackway land :afsiibe' scriber of a public telephone system fby space carriere' telephoneeqiiipnient lia-ving "a limitenl efr fective range of i-,ifansinisfsioni a eneatersta-ticn located. between said 4texlrninal stations, said vehicle andrepea'teiv station each provided withsaid space telephone equipment; 'a `public telephone system connection at each of 'said terminal fstae tions, a control linecircit' for each of said' ters minal stations,` eachsaid control lline circuit' ein; tending from its terminal station tofsaid' repeater station and 'including a sourceof current fandzr manually operable switching 'means'` at tire.u e# spective terminalstation `and a control 'relayft therepeatery station, coupling vmeans for eachl'fot saidfterninal stations-land each Vsaid 'couplin mean-sincluding :contacts of the switching means' and'vof the sontrolirelay -for said line "ccnitfot the samelterrninal station and being.effective'tot times to couple said space telephone equipment'of f the' repeater station Ato saidfpublic telephoner-System connection"of the respective" terminal sta#- tion; lockoutmeansfor 'each terminallstationland each said lockoiitffmeans including amanually operable-switch atfthe respective terminal.feta;`` tion, another line circuit and alock relayrat they opposite terminal station; VAand circuit#'mear'ist each said terminal station including contacts yofk thev lock relay located'at the same terminal l"staf tion to render said coupling means oftherespecei tive terminal station neiective.

-lELBERT im MARLQWE;l

REFERENCES vCITED The foiiwin'g references: are ycf ieeord-fintne-- nie of-tiiis patent: Y

UNIT' ED "STATES 'ATET' 

